Automatic System for Adjusting the Parabolic Surface of a Flat Mirror Solar Concentrator

ABSTRACT

The invention relates to a system for the automatic adjustment of the height of the support elements of a structure of a solar concentrator, in order to achieve the approximation of a parabolic surface for mounting triangular mirrors. These adjustments are made by an automatic arm with a control unit based on computer vision, wherein the system displays the adjustment embodiment with a magnetic or pneumatic head that uses a control unit whose operation is based on stereo vision images with signals from one or more digital cameras.

FIELD OF THE INVENTION

The present invention relates to an automatic adjustment system for the height of the support elements, which are arranged in a structure in order to achieve the approximation of a parabolic surface of triangular mirrors of a solar concentrator.

BACKGROUND OF THE INVENTION

The document (1) describes a triangular flat mirror parabolic concentrator, where screws are used to adjust the heights of the vertices of each triangular mirror, where each screw can move six vertices of the neighbor triangles. The adjustment of height is done by directing the reflected solar beam from the mirrors to a focal point. This method is very complicated, because the movement of one screw simultaneously affects in parallel to six neighboring minors. Also, to focus all the mirrors is necessary to solve many linear equations explicitly, or to use many sequential approaches.

The adjustment method of the mirrors described in the document [2] describes a design, wherein each mirror has two rotational axes; similarly, the position adjustment of each mirror is done manually using reflected beam of light. In this case, the adjustment of one mirror does not influence to the positions of the other mirrors and this simplifies the process of adjustment. However, the limitation of this method is that the manual adjustment of the position of each mirror is labor costly.

In the patent application [3], a ruler with parabolic curvature in its lower part (FIG. 1) is proposed that rotates over the parabolic structure of the support of the mirrors; said ruler rotates about the vertical axis in the center of the structure to perform a scanning of the structure surface to identify and adjust the height of each of the adjustment screws that fixing the mirrors to obtain the parabolic surface. The disadvantage of this method is that the adjustment is still performed manually.

As can be seen, there is a need to develop a system that performs automatically the necessary review and/or correction of the adjustment elements located on the surface of the concentrator structure, in order to correct the height position of each adjustment element and thereby ensure the curvature of the surface of the parabolic concentrator.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1. Shows a support of a solar concentrator with a manual adjustment ruler of the prior art.

FIG. 2. Shows the automatic adjustment device of the parabolic surface.

FIG. 3. Shows the telescopic tube to rotate the adjusting elements with an end-effector embodiment with a magnetic head.

FIG. 4. Shows the telescopic tube to rotate the adjusting elements with an end-effector embodiment with a pneumatic head.

FIG. 5. Shows the system in the B, C, and D embodiments using 2, 3, or 6 telescopic tubes respectively.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a system for automatic review and/or correction of the height of the support elements of a structure of a parabolic concentrator to support flat mirrors. Said system uses an automatic arm (A) as is shown in (FIG. 2), which has a vertical axis in the central point of the parabolic structure, on which a central tube (5) is installed that is capable of rotating 360° about its axis.

To rotate the automatic arm (A) an actuator (8) is included, which can be an engine with a gears box. The automatic arm (A) has a carriage (9), which can move on the solar concentrator (1) radially respect to the central tube (5) using at least one guide or shaft on which is moved; FIG. 2 shows the embodiment comprising two parallel guides (11). Over said carriage (9) supports the following elements: at least one digital camera (10), one, two, three, or six telescopic tubes (12); said telescopic tubes (12) have a rotational motion about their axis and support on their distal part, an end-effector that is coupled with the support elements (4) comprising a thread and adjust to the desired position when rotated.

Said system has a control unit responsible for processing the information from the digital camera (10); this information is delivered in image format and subject to digital processing to compute the initial size of the support element (4) using specific algorithms to obtain the size/height ratio of the support element (4); its height depends on the size of the image (4); when the size of the image exceeds a pre set range in the control unit, this indicates that the support element (4) should be adjusted to lower the height. On the contrary, if the size of the image is smaller than the reference, the height of said support element (4) should be raised. The control algorithm determines the number of turns required of the telescopic tube (12), whether full or fractional, to achieve the desired height.

One embodiment includes the use of two digital cameras whose captured images generate a stereovision signal to determine the original height of the support elements (4) and make adjustments if required.

The telescopic tube (12), as shown in FIG. 3, comprises: an inner tube (14), an outer tube (15), a bottom base (16), a telescopic-tube engine (17), an upper base (18), a coupling gear (19), a rotating gear (20), a rack (21), a gear for height adjustment (22), a gear box (23), an engine for height adjustment (24), and has at its terminal an end-effector, which can be coupled with an electromagnetic head (13) or a pneumatic head (25) (as is shown in FIG. 4).

The outer tube (15) is coupled with the bottom base (16) whereby it can move backward and forward. The rack (21) is fixed to the outer tube (15) and is coupled with the gear for height adjustment (22), which is connected to the gear box (23) and the engine, for height adjustment (24). The gear box (23), the engine for height adjustment (24), and the gear for height adjustment (22) are supported on the bottom base (16). These elements have the backward and forward movement with the automatic arm (A).

The upper base (18) is fixed to the upper end of the outer tube (15), and on the upper base (18) the engine of the telescopic tube (17) is fixed with the coupling gear (19), which is engaged with the rotation gear (20), which connects to the upper end of the inner tube (14); these elements allow the rotation of the telescopic tube (12) and consequently of the end-effector, which is coupled with the lower end of the inner tube (14).

To provide all the support elements (4) to the desired height in order to achieve the parabolic surface, the system has the following operation mode:

-   1. Upon system startup, the carriage (9) supporting the telescopic     tube and at least one digital camera (10) is positioned over a first     support element (4). -   2. The control unit activates the digital camera (10) and captures a     first image. -   3. The control unit receives the information and calculates with the     control algorithm the initial height of the first support element     (4); the information received is compared to a reference so to     determine whether the element is above or below the level of height     needed to generate the curve of the parabola. -   4. If the element is below of the pre set height, the control unit     sends a signal to the telescopic tube to descend and position itself     over the support element (4) to be adjusted. -   5. After completing the alignment between the telescopic tube (12)     and the support element (4), the end-effector is coupled to the     support element (4), using an electromagnetic head (13) or a     pneumatic head (25). -   6. Depending on the initial height of the support element (4), the     telescopic tube rotates clockwise or counterclockwise, until the     adjustment element achieves its indicated position, due its thread. -   7. Subsequently, the rotation of the telescopic tube is stopped and     the end-effector of the support element (4) is disengaged. -   8. The robotic arm elevates its telescopic tube (12) is raised, and     the same operation is performed over the next support element (4). -   This operation is performed for each support element (4) to obtain     the desired height in each of them, thereby achieving the curvature     of the parabolic surface of the solar concentrator.

In one embodiment, the control unit of the system can use the signals from more than one digital camera (10), using algorithms of computer vision defined to identify and process each signal from each camera to determine the height of the support element (4) based on the image size.

As a demonstrative example but not limiting of the scope of the present invention, we describe one mode of operating the system by using the electromagnetic head (13) as the end-effector:

When the device is turned on, the central tube (5) begins its rotational motion on the structure, starting its operation of tracking or detection of the positions of the support elements (4) by two digital cameras (10); when the digital cameras are positioned over a first adjustment point, they send an image to the control unit generating a stereo vision image; after processing the image, the initial height of the support element (4) is determined; if the height is above or below its pre set height, the control unit sends a signal to descend the telescopic tube (12) allowing to position itself on the detected support element (4). Once the positioning is achieved, the downward movement of the telescoping tube (12) is interrupted and the electromagnetic head (13) is energized to couple with the support element (4); at which point, the engine of the telescopic tube (17) begins to rotate and consequently, the electromagnetic head (13) with the support element (4) are rotating too and support element (4) travels up or down.

When the desired adjustment is achieved, the supply to the electromagnetic head (13) is interrupted, disengaging it from the support element (4). The gear box (23) connects to the gear for height adjustment (22) and the engine for height adjustment (24), which rotates the gear for height adjustment (22) counterclockwise, and the outer tube (15) is displaced up. This completes the position adjustment of a support element (4). This process is performed for each support element (4).

In another embodiment of the telescopic tube, a pneumatic head (25) can be employed, using the elements of the structure mentioned above by adding an air bleed tube (26) for the operation of the pneumatic head (25), which is coupled with the support element (4) by generating a vacuum.

In other embodiments, the system can use 2, 3, or 6 telescopic tubes in parallel, as show in the corresponding embodiments B, C and D of FIG. 5, wherein the symmetry of the support structure is used to reduce the adjustment time.

REFERENCES

[1] Wood Douglas, Support structure for a large dimension parabolic reflector and large dimension parabolic reflector, EP 002288 A1 (Wood Douglas) Dec. 21, 1982 (Jul. 24, 1979).

[2] Estufa solar para poblaciones urbanas, del Departamento de Ingeniería Eléctrica del Centro de Investigación y Estudios Avanzados (Cinvestav) México, http://pepegrillo.com/2009/02/estufa-solar-para-poblaciones urbanas/.

[3] Kussul E., Baidyk., Lara-Rosano F., Saniger J. M., Gasca G., Bruce N., Method and device for mirrors position adjustment of a solar collector, US Patent Application 20110215073, Mar. 2, 2011 (MX/A/2010/002418, Feb. 3, 2010). 

1. An automatic system to adjust the parabolic surface of flat mirror solar concentrator, characterized because said solar concentrator comprises a central tube arranged over the vertical axis from the center of a support structure of the solar concentrator; said tube allows a 360° rotation of an automatic arm, which is supported perpendicularly to the axis of the central tube on the upper part of said central tube; also, the automatic arm has a coupled engine for height adjustment, a gears box and a gear for height adjustment, wherein these elements provide a vertical displacement up and down; in its upper part, the automatic arm has at least one guide arranged perpendicularly to the central tube; on said guide a carriage slides radially to the solar concentrator; said carriage supports at least one digital camera and at least one telescopic tube, wherein said telescopic tube is fixed and arranged in parallel to the central axis on the carriage and includes an engine for telescopic adjustment, a coupling gear, and a rotation gear; these elements allow the rotation of the telescopic tube about its axis; finally, at the distal extreme of said telescopic tube there is an end-effector for adjusting the height of the support elements of the solar concentrator.
 2. The automatic system of claim 1, characterized because can use 2, 3 or 6 parallel telescopic tubes, supported by the automatic arm making use of the symmetry of the support structure.
 3. The automatic system of claim 1, characterized because the control unit can use the signals from one or more digital cameras using computer vision defined algorithms to identify the height of the support element based on their size in the image or on the stereovision principles.
 4. The automatic system of claim 1, characterized because the end-effector can be an electromagnetic head.
 5. The automatic system of claim 1, characterized because the end-effector can be a pneumatic head for which an air bleed tube is added. 